C S Sundar
Articles written in Pramana – Journal of Physics
Volume 13 Issue 6 December 1979 pp 625-636 Solids
Positron lifetime has been measured as a function of temperature in Sidoped GaAs single crystals subjected to various heat treatments. Defects produced by these heat treatments trap positrons. In all the GaAs samples containing defects positron lifetime was found to decrease with temperature in the range from 375 K to 16 K. The decrease is explained as due to the decrease in the trapping rate. The trapping rate is mainly controlled by the diffusion of the positron to the trap. The diffusion constant is determined mainly by the scattering from charged Si impurities.
Volume 42 Issue 5 May 1994 pp 375-385
The structure of multilayered carbon tubules has been investigated by electron microscopy and X-ray diffraction. The structure of tubules is characterized by disorder in the stacking of cylindrical graphene sheets. Raman scattering measurements have been carried out in tubules and compared with graphite. The observed features in the Raman spectra in tubules can be understood in terms of the influence of disorder. The additional Raman modes predicted for single layer carbon tubules have not been observed.
Volume 67 Issue 1 July 2006 pp 153-162
Nickel substitution at the cobalt site in Na0.75CoO2 induces an upturn in the resistivity on lowering the temperature, with the metal-to-insulator transition temperature (
Volume 97, 2023
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